HAMILTON — A collision involving a charter bus, a dump truck and a car on the New Jersey Turnpike yesterday morning left four people injured, and brought traffic to an hours-long standstill in all northbound lanes of the highway, the State Police said.

Rachael Athay, 28, and Elinor Athay, 66, both of Woodbridge, Va., had to be freed from their car by firefighters.

They were both in stable condition at Capital Health Regional Medical Center in Trenton last night, according to hospital staff. The two others involved in the crash suffered minor injuries.

The vehicles were northbound on the Turnpike about two miles south of Interchange 7A around 9:30 a.m. when the dump truck struck the car, causing the car to hit a charter bus operated by the Megabus company.

The dump truck then also hit the Megabus, said Sgt. Adam Grossman, a State Police spokesman.

Troopers arriving on scene found the car facing west in the center lane and the dump truck and Megabus, with 47 passengers aboard, in the right lane, Grossman said.

The Athays were taken to Capital Health suffering internal and head injuries. The driver of the dump truck, identified as 54-year-old Elizabeth resident Eduardo Ayala, suffered a head injury and laceration to his face and was taken to Robert Wood Johnson University Hospital in Hamilton, the State Police said.

Desserie Shaw and Jerard Shaw, both residents of Bear, Del., who were in the Megabus, were taken to the Hamilton hospital as well. Desserie Shaw complained of chest pain, while Jerard Shaw complained of neck and back pain, according to the State Police. Zia Khokhar, the Megabus driver, was uninjured.

The condition of Rachael and Elinor Athay was initially believed to be serious enough that authorities called for a medevac helicopter to take them to the hospital.

The helicopter could not fly due to the weather, the State Police said.

Troopers closed the Turnpike lanes at 9:40 a.m. and reopened them around 3:30 p.m. Backups along the highway were reported to span several miles through the late morning yesterday. Traffic was moving normally through the area by 5 p.m.

The collision remains under investigation, and no summonses had been issued as of late yesterday.